PRF1 and neoplasm: The inhibition of STAT1 phosphorylation represses upregulation of PD-L1 by IFN-γ, whereas the inhibition of STAT3 phosphorylation decreases the production of immunosuppressive cytokines by tumor cells, resulting in the conversion of tumor-mediated immune suppression to activation of T cells, as well as increased infiltration of CD8+ T cells and expression of T-bet, IL-21, perforin, and FasL [147].